Rheumatoid arthritis (RA) is a chronic inflammatory arthropathy affecting approximately 1% of the general population worldwide. The disease is characterized by symmetrical inflammation of the synovial lining of diarthrodial joints, leading to cartilage and bone destruction and resulting in significant morbidity. Despite advances in RA treatment, many patients fail to respond to current therapy. Over half of the patients who initially respond eventually cease therapy due to secondary loss of efficacy and/or life-threatening toxicities. Many of these patients will ultimately require costly joint replacement to improve and maintain their daily activities. These problems highlight the need for continued development of additional therapies for RA. Unlike conventional drugs, nanosystems allow targeted delivery of a small but concentrated amount of therapeutic agents specifically to the desired site of inflammation. In addition, these nanosystems allow non-invasive and quantitative image-based readouts of drug effects, which ultimately translate to improved outcomes while minimizing systemic side effects. Using perfluorocarbon nanoparticles that target the integrin 1v23 on neovasculature, we delivered the anti-angiogenic drug fumagillin to arthritic mice. Our preliminary data indicate that 1v23-targeted perfluorocarbon nanoparticles halt the progression of inflammatory arthritis in a mouse model of RA. To further explore the use of nanoparticles for therapy and non-invasive evaluation of early treatment response in inflammatory arthritis, we propose the following aims: Specific Aim 1: Develop systemic targeted nanomedicine strategies to halt or reverse inflammation in a mouse model of arthritis. Using a collagen-induced arthritis (CIA) model, we have determined that systemic injection of 1v23-targeted nanoparticles carrying fumagillin into arthritic mice led to >50% decrease in joint inflammation. These preliminary studies suggest that targeted nanoparticles may represent a novel way to treat RA and other types of inflammatory arthritis. However, many issues regarding the therapeutic agent selection, the dose, the administration strategy, and the use of adjunctive treatment remain unresolved. In this aim, we will test how different nanoparticle formulations, targeting and administration strategies will impact on the progression of inflammation in murine CIA. Specific Aim 2: Develop intra-articular nanomedicine strategies to halt and inhibit cartilage and bone erosions. Intra-articular injection is an attractive alternative in treating RA because of the much lower total dose of medication given by local delivery. Yet despite the limitations of systemic administration of disease modifying drugs, intra-articular injections have not been actively investigated because of the rapid clearance of drugs from the joint and the short-lived beneficial effect. Due to their size, nanoparticles are well suited for intra-articular use because the drugs entrapped in the outer surfactant layer are restricted to the joint space, allowing specific and local delivery of drugs without systemic effects. We will develop nanoparticle formulations that target proliferative synovium to reverse pannus formation and inhibit cartilage and bone erosions in a rabbit model of inflammatory arthritis and evaluate these in combination with systemic nanoparticle approaches. In conjunction, we will develop MR molecular imaging technologies based on targeted nanoparticles to track early therapeutic responses in a rabbit model of inflammatory arthritis.